Method for illuminating a substrate using multiple acoutso optical devices

ABSTRACT

A method and a system for illuminating a substrate, the system may include an acousto-optic device (AOD); and an etendue expanding optical module. The AOD may include a surface having an illuminated region; wherein the illuminated region is configured to receive a collimated input beam while being fed with a control signal that causes the illuminated region to output illuminated region output beams that are collimated and exhibit deflection angles that scan, during a scan period, a deflection angular range. The etendue expanding optical module is configured to convert the illuminated region output beams to collimated output beams that impinge on an output aperture; wherein a collimated output beam has a width that exceeds a width of an illuminated region output beam; and wherein the etendue expanding optical module comprises a Dammann grating that is configured to output diffraction patterns, each diffraction pattern comprises diffraction orders that cover a continuous angular range.

BACKGROUND

A variety of systems are used for automated inspection of semiconductorwafers, in order to detect defects, particles and/or patterns on thewafer surface as part of a quality assurance process in semiconductormanufacturing processes. It is a goal of current inspection systems tohave high resolution and high contrast imaging in order to provide thereliability and accuracy demanded in sub-micron semiconductormanufacturing processes. However, it is also important to have ahigh-speed process that permits a large volume throughput so that thequality and assurance processes do not become a bottleneck in the waferproduction process. Accordingly, the optical inspection systems must useshorter wave lengths, higher numerical aperture optics and high densityimage capture technology in order to enable the processing of data fromsuch systems at sufficiently high rates that will satisfy the desiredproduct throughput requirements.

Higher numerical aperture values allows to visualize finer details.Higher field of view allow to increase the throughput of the system.

U.S. Pat. No. 7,053,395 illustrates a wafer detection system thatincludes a traveling lens acousto-optic device that has an activeregion. An input beam illuminates the entire active region and a RFinput signal is applied to the active region to selectively generateplural traveling lenses in the active region. The plural travelinglenses focuses the input beam to generate plural flying spot beams, atthe respective focus of each of the generated traveling lenses. The areaof an illuminated surface of the active region well exceeds theaggregate area of the plural traveling lenses—thus reducing the energyusage efficiency of the system.

This leads to a reduction in the overall etendue of the waferdetection—thereby limiting a low numerical aperture (NA) and/or a smallfield of view.

There is a growing need to provide a highly effective system and methodfor focusing a beam on a substrate.

SUMMARY

There may be provided a method, and a system for illuminating asubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the embodiments of the disclosure isparticularly pointed out and distinctly claimed in the concludingportion of the specification. The embodiments of the disclosure,however, both as to organization and method of operation, together withobjects, features, and advantages thereof, may best be understood byreference to the following detailed description when read with theaccompanying drawings in which:

FIG. 1 illustrates an example of a system;

FIG. 2 illustrates an example of a system;

FIG. 3 illustrates an example of a method;

FIG. 4 illustrates an example of a system;

FIG. 5 illustrates an example of a system; and

FIG. 6 illustrates an example of a method.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the embodiments ofthe disclosure.

However, it will be understood by those skilled in the art that thepresent embodiments of the disclosure may be practiced without thesespecific details. In other instances, well-known methods, procedures,and components have not been described in detail so as not to obscurethe present embodiments of the disclosure.

The subject matter regarded as the embodiments of the disclosure isparticularly pointed out and distinctly claimed in the concludingportion of the specification. The embodiments of the disclosure,however, both as to organization and method of operation, together withobjects, features, and advantages thereof, may best be understood byreference to the following detailed description when read with theaccompanying drawings.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

Because the illustrated embodiments of the disclosure may for the mostpart, be implemented using electronic components and circuits known tothose skilled in the art, details will not be explained in any greaterextent than that considered necessary as illustrated above, for theunderstanding and appreciation of the underlying concepts of the presentembodiments of the disclosure and in order not to obfuscate or distractfrom the teachings of the present embodiments of the disclosure.

Any reference in the specification to a method should be applied mutatismutandis to a system capable of executing the method.

Any reference in the specification to a system should be applied mutatismutandis to a method that may be executed by the system.

The term “and/or” means additionally or alternatively.

There may be provided systems and methods that may increase the etendueand allow systems with higher throughput and also may exhibit a betterenergy efficiency.

For simplicity of explanation the same reference numbers may be sued todescribe a single element and a plurality of said elements.

It should be noted that the figures illustrate beams at a certain pointin time. A single beam of a certain figure may be scanned or otherwisechanged over time and can be referred to as a beam or as beams.

Single AOD

FIGS. 1 and 2 illustrates system 10 at two different points of time. Thetwo points of time represent a start and an end of a scan period. Thesystem may scan a region (for example a line) of a substrate during ascan period. The system may perform multiple scans during multiple scanperiods. During the multiple scan periods a movement may be introducedbetween the system (or at least the optics of the system) and thesubstrate.

System 10 may be configured to illuminate the substrate. System 10 mayalso be configured to detect radiation from the substrate. System 10 mayalso be configured to evaluate the substrate—for example performinspection, defect detection and/or any other evaluation of thesubstrate.

The illumination path of the system may perform multiple types ofscans—where one scan may be converted to another scan. FIG. 1illustrates angular scanning (see arrows 11 and 14 that represent theangular scan), and linear scanning (see arrows 12, 13, 15 and 16 thatrepresent the linear scan). The linear scanning may be along the x-axisof the figure or along any other axis. Any angular range illustrated inFIG. 1 may be of any value. Any linear scan may scan along a scan pathof any length.

In FIG. 1, the system 10 is illustrated as including a light source 20,an acousto-optic device (AOD) 30 that is controlled by control signal 77sent from controller 94, an etendue expanding optical module 70 and anoutput module 75.

The AOD 30 has a surface 31 having an illuminated region 32. Theilluminated region 32 is configured to receive a collimated input beam(from the light source 20) while the AOD is being fed with controlsignal 77.

The area of the illuminated region 32 is a fraction (for example—lessthan 30, 20, 10, 5, 1 percent) of an area of the surface 31. Theradiation source may be configured to avoid illuminating the surfaceoutside the illuminated region.

Control signal 77 causes the illuminated region 32 to output illuminatedregion output beams 82 that are collimated and exhibit deflection anglesthat scan, during a scan period, a deflection angular range (see arrow11).

The rightmost deflection angle of the deflection angular range is shownin FIG. 1. The leftmost deflection angle of the deflection angular rangeis shown in FIG. 2.

The deflection angular range may be less than one degrees or more than1, 5, 10, 20, 25, 30, 35, 40, 45, 50 degrees and even more.

The etendue expanding optical module 70 is configured to convert theilluminated region output beams 82 to collimated output beams 87 thatimpinge on an output aperture 54.

Different collimated output beams exhibit different angles ofimpingement (see arrow 14). The leftmost tilted collimated output beamis shown in FIG. 1. The rightmost tilted collimated output beam is shownin FIG. 2.

A collimated output beam has a width (the width may be measured alongthe x-axis of the figure) that exceeds a width of an illuminated regionoutput beam.

The etendue expanding optical module 70 includes a Dammann grating 44that is configured to output diffraction patterns 86. Each diffractionpattern includes diffraction orders (such as first diffraction order86(1), second diffraction order 86(2) and third diffraction order 86(3))that cover a continuous angular range. The diffractions orders maypartially overlap or may not-overlap but formed without a gap betweenthem. The number of diffraction orders may be two or may exceed three.

In FIG. 1, the etendue expanding optical module 70 also includes (i) acylindrical lens 40 that precedes the Dammann grating, and (b) aspherical lens 48 that follows the Dammann grating.

The Dammann grating is located at a back focal plane of the sphericallens 48 and at the front focal plane of the cylindrical lens 40.

The cylindrical lens 40 is configured to focus the illuminated regionoutput beams 82 onto the Dammann grating to provide focused beams 84′.

Focused beams of different deflection angles impinge on differentlocations of the Dammann grating, during the scan period.

The rightmost focused beam is shown in FIG. 1. The leftmost focused beamis shown in FIG. 2.

The Dammann grating 44 is configured to illuminate the spherical lens 48with the diffraction patterns. Different diffraction patterns impinge ondifferent locations of the spherical lens 48, during the scan period.

The rightmost diffraction patterns is shown in FIG. 1. The leftmostdiffraction patterns is shown in FIG. 2.

The system 10 has an output aperture 54 that is located at a front focalplane of the spherical lens 48. The spherical lens is configured toconvert, during the scan period, the diffraction patterns to thecollimated output beams 87.

The leftmost tilted collimated output beam is shown in FIG. 1. Therightmost collimated output beam is shown in FIG. 2. The angular rangeof the tilt is illustrated by arrow 14.

System 10 may include an output module 75. The output module 75 isconfigured to convert the collimated output beams 87 to spaced apartspots (such as 89′(1) and 89′(K)) on the substrate 99.

Different linear array of spots scan a linear region of the substrateduring the scan period. The scan can be along the x-axis of the figure.

FIG. 1 illustrates the output module as including output Dammann grating58 and objective lens 49.

The output Dammann grating 58 is configured to receive the collimatedoutput beams 87, and provide output diffraction patterns (such as88(1)-88(K)) that are converted by the objective lens 49 to focusedoutput beams (such as 89(1)-89(K)) that form spaced apart spots (such as89′(1) and 89′(K)) on the substrate. The focused output beam perform alinear scan—see arrow 15.

It should be noted that each collimated output beam 87 includes multiple(K) rays—and for simplicity of explanation only the rightmost ray andthe leftmost ray were illustrated. The rays are located between therightmost ray and the leftmost ray.

For simplicity of explanation FIG. 1 illustrates only the rightmostfocused output beam 88(K), the leftmost focused output beam 88(1), therightmost spot 89′(1), and the leftmost spot 89′(K).

The focused output beam and the spots may linearly scan the substrate99—see arrow 16.

FIG. 1 also illustrates the system 10 as including beam splitter 60, oneor more detectors 90, processing circuit 92 and controller 94.

The one or more detectors 90 are configured to generate detectionsignals indicative of radiation from the substrate that resulted from aformation of the spaced apart spots on the substrate. The radiation mayimpinge on beam splitter 60 and be directed (see arrow 95) towards theone or more detectors 90.

The processing circuit 92 may perform defect detection, or any othermeasurement or evaluation related to the substrate.

FIG. 3 illustrates an example of a method 300 for illuminating asubstrate.

Method 300 may start by step 310 of illuminating an illuminated regionof a surface of an active region of an acousto-optic device with acollimated input beam while feeding the acousto-optic device with acontrol signal that causes the illuminated region to output illuminatedregion output beams that are collimated and exhibit deflection anglesthat scan, during a scan period, a deflection angular range.

An area of the illuminated region is a fraction of an area of thesurface, and the method may include avoiding from illuminating thesurface outside the illuminated region.

Step 310 may be followed by step 320 of receiving the illuminated regionoutput beams by an etendue expanding optical module.

Step 320 may be followed by step 330 of converting the illuminatedregion output beams, by the etendue expanding optical module, tocollimated output beams that impinge on an output aperture. Thecollimated output beam has a width that exceeds a width of anilluminated region beam.

Step 330 may include steps 332, 334 and 336.

Step 332 may include focusing the illuminated region output beams, by acylindrical lens of the etendue expanding optical module, onto a Dammanngrating to provide focused beams.

The Dammann grating may be located at a back focal plane of a sphericallens.

Focused beams of different deflection angles impinge on differentlocations of the Dammann grating, during the scan period.

Step 334 may include outputting diffraction patterns, by the Dammanngrating. Each diffraction pattern may include diffraction orders thatcover a continuous angular range.

Step 334 may also include illuminating a spherical lens of the etendueexpanding optical module with the diffraction patterns, by the Dammanngrating.

Different diffraction patterns impinge on different locations of thespherical lens, during the scan period.

Step 336 may include converting, by the spherical lens and during thescan period, the diffraction patterns to the collimated output beams.The collimated output beams impinge on an output aperture that islocated at a front focal plane of the spherical lens.

Step 330 may be followed by step 340 of converting, by an output module,the collimated output beams to spaced apart spots on the substrate.

Different linear array of spots scan a linear region of the substrateduring the scan period.

Step 340 may include steps 342, 344 and 346.

Step 342 may include illuminating an output Dammann grating with thecollimated output beams.

Step 344 may include outputting, by the output Dammann grating, outputdiffraction patterns.

Step 346 may include converting the output diffraction patterns, by anobjective lens, to form the spaced apart spots.

Step 340 may be followed by step 350 of obtaining detection signalsindicative of radiation from the substrate that resulted from aformation of the spaced apart spots on the substrate.

Steps 310, 320, 330 may be repeated for each one of multiple scanperiods. The same applied to steps 310, 320, 330, 340 and 350.

Multiple AODs

FIGS. 4 and 5 illustrate system 10, at two different points of time thatrepresent a start and an end of a scan period. The system may scan aregion (for example a line) of a substrate during a scan period. Thesystem may perform multiple scans during multiple scan periods—while amovement is introduced between the system and the substrate.

System 10′ may be configured to illuminate the substrate. System 10′ mayalso be configured to detect radiation from the substrate. System 10′also be configured to evaluate the substrate—for example performinspection, defect detection and/or any other evaluation of thesubstrate.

FIG. 4 illustrates angular scanning (see arrows 11′ and 14′ thatrepresent the angular scan), and linear scanning (see arrows 12′, 15′and 16′ that represent the linear scan). The linear scanning may be along the x-axis of the figure or along any other axis. Any angular rangeillustrated in FIG. 1 may be of any value. Any linear scan may scanalong a scan path of any value.

In FIG. 4 the system 10 is illustrates as including a light source 20,acousto-optic devices (AODs) 30(1)-30(N) —each is controlled (by controlsignal 77 sent from controller 94), relay module 79 and an output module75.

Each AOD has a surface having an illuminated region. For example—see AOD30(n), n ranges between 1 and N. AOD 30(n) has surface 31 andilluminated region 32. The N illuminated regions are configured toconcurrently receive a collimated input beam (80(1)-80(N) from the lightsource 20) while the AOD is being fed with control signal 77.

The area of each illuminated region 32 is a fraction (for example—lessthan 30, 20, 10, 5, 1 percent) of an area of each surface 31. Theradiation source may be configured to avoid illuminating the surfacesoutside the illuminated regions.

For each AOD of AODs 30(1)-30(N) —a control signal 77 causes theilluminated region 32 to output illuminated region output beams (such as81(1)-81(N)) that are added by the optical combining module to providecombined beams (such as combined beam 81—one combined beam at a time),whereas each combined beam covers a continuous angular range.

System 10′ may also include relay module 79 that images an output planeof the optical combining module 34 onto an output aperture 54 of thesystem.

A combined beam 81 impinges on cylindrical lens 40 that converts thecombined beam 81 to an intermediate collimated beam 84. The intermediatecollimated beam 84 impinges on the spherical lens 48 that outputs anoutput collimated beam onto the output aperture 54.

The different combined beams exhibit, at the output plane of the opticalcombining module, different deflection angles—as illustrated by arrow11′. The different deflection angles cause the different combined beamsto impinge on different locations of the cylindrical lens 40—to performa linear scan—see arrow 12′. Different output collimated beams impingeon the output aperture 54 at different angles—as shown in arrow 14′.

System 10′ may include an output module 75. The output module 75 isconfigured to convert the collimated output beams (such as collimatedoutput beam 87) to spaced apart spots (such as 89′(1) and 89′(K)) on thesubstrate 99.

Different linear array of spots scan a linear region of the substrateduring the scan period. The scan can be along the x-axis of the figure.

FIG. 4 illustrates the output module as including output Dammann grating58 and objective lens 49.

The output Dammann grating 58 is configured to receive the collimatedoutput beams (such as output collimated beam 87), and provide outputdiffraction patterns (such as 88(1)-88(K)) that are converted by theobjective lens 49 to focused output beams (such as 89(1)-89(K)) thatform spaced apart spots (such as 89′(1) and 89′(K)) on the substrate.

It should be noted that each collimated output beam 87 include multiple(K) rays—and for simplicity of explanation only the rightmost ray andthe leftmost ray were illustrated. The rays range between the rightmostray and the leftmost ray. For simplicity of explanation FIG. 4illustrated only the rightmost focused output beam 88(K), the leftmostfocused output beam 88(1), the rightmost spot 89′(1), and the leftmostspot 89′(K). The focused output beam perform a linear scan—see arrow15′.

The focused output beams and the spots may linearly scan the substrate99—see arrow 16′.

FIG. 4 also illustrates the system 10′ as including beam splitter 60,one or more detectors 90 and a processing circuit 92.

The one or more detectors 90 are configured to generate detectionsignals indicative of radiation from the substrate that resulted from aformation of the spaced apart spots on the substrate. The radiation mayimpinge on beam splitter 60 and be directed towards the one or moredetectors 90.

FIG. 4 also illustrates a combiner 34(1) that is illuminated by firstAOD 30(1) and second AOD 30(2). The combiner 34(1) may include a prism35(3), a first lens 35(1) and a second lens 35(3). Other combiners maybe used.

FIG. 5 illustrates an optical combining module 34 that adds the outputsof eight AODs—30(1)-30(8). The optical combining module 34 includesmultiple (for example five) combiners—including first level combiners34(1) for adding the outputs of two AODs each, second level combiners34(2) for combining the outputs of two first level combiners each, and athird level combiner 34(3) for combining the outputs of two second levelcombiners each to output the combined beam.

FIG. 6 illustrates method 600 for illuminating a substrate.

Method 600 may start by step 610 of illuminating, concurrently,illuminated regions of acousto-optic devices with collimated input beamswhile concurrently feeding the acousto-optic devices with controlsignals that cause the illuminated regions to concurrently outputilluminated regions output beams that are collimated and exhibitdeflection angles that scan, during a scan period, a deflection angularrange.

Step 610 may be followed by step 620 of combining, by an opticalcombining module, the illuminated regions output beams to providecombined beams (one at a time), each combined beam covers a continuousangular range. Different combined beams exhibit, at the output plane ofthe optical combining module, different deflection angles.

Step 620 may be followed by step 630 of imaging, by a relay module, anoutput plane of the optical combining module onto an output aperture ofthe system.

Step 630 may include steps 632 and 634.

Step 632 may include converting, by a cylindrical lens of the relaymodule, the combined beams to intermediate collimated beams. Differentintermediate collimated beams impinge on different parts of thespherical lens.

Step 634 may include outputting, by the spherical lens, collimatedoutput beams towards the output aperture.

Step 630 may be followed by step 640 of converting, by an output module,the collimated output beams to spaced apart spots on the substrate.

Different linear array of spots scan a linear region of the substrateduring the scan period.

Step 640 may include steps 642, 644 and 646.

Step 642 may include illuminating an output Dammann grating with thecollimated output beams.

Step 644 may include outputting, by the output Dammann grating, outputdiffraction patterns.

Step 646 may include converting the output diffraction patterns, by anobjective lens, to form the spaced apart spots.

Step 640 may be followed by step 650 of obtaining detection signalsindicative of radiation from the substrate that resulted from aformation of the spaced apart spots on the substrate.

Steps 610, 620, 630 may be repeated for each one of multiple scanperiods. The same applied to steps 610, 620, 630, 640 and 650.

In the foregoing specification, the embodiments of the disclosure hasbeen described with reference to specific examples of embodiments of thedisclosure. It will, however, be evident that various modifications andchanges may be made therein without departing from the broader spiritand scope of the embodiments of the disclosure as set forth in theappended claims.

Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under”and the like in the description and in the claims, if any, are used fordescriptive purposes and not necessarily for describing permanentrelative positions. It is understood that the terms so used areinterchangeable under appropriate circumstances such that theembodiments of the disclosure described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

The connections as discussed herein may be any type of connectionsuitable to transfer signals from or to the respective nodes, units ordevices, for example via intermediate devices. Accordingly, unlessimplied or stated otherwise, the connections may for example be directconnections or indirect connections. The connections may be illustratedor described in reference to be a single connection, a plurality ofconnections, unidirectional connections, or bidirectional connections.However, different embodiments may vary the implementation of theconnections. For example, separate unidirectional connections may beused rather than bidirectional connections and vice versa. Also,plurality of connections may be replaced with a single connection thattransfers multiple signals serially or in a time multiplexed manner.Likewise, single connections carrying multiple signals may be separatedout into various different connections carrying subsets of thesesignals. Therefore, many options exist for transferring signals.

Any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the above described operations merely illustrative. The multipleoperations may be combined into a single operation, a single operationmay be distributed in additional operations and operations may beexecuted at least partially overlapping in time. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

Also for example, in one embodiment, the illustrated examples may beimplemented as circuitry located on a single integrated circuit orwithin a same device. Alternatively, the examples may be implemented asany number of separate integrated circuits or separate devicesinterconnected with each other in a suitable manner.

However, other modifications, variations and alternatives are alsopossible. The specifications and drawings are, accordingly, to beregarded in an illustrative rather than in a restrictive sense.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The word ‘comprising’ does notexclude the presence of other elements or steps then those listed in aclaim. Furthermore, the terms “a” or “an,” as used herein, are definedas one or more than one. Also, the use of introductory phrases such as“at least one” and “one or more” in the claims should not be construedto imply that the introduction of another claim element by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim element to embodiments of the disclosure scontaining only one such element, even when the same claim includes theintroductory phrases “one or more” or “at least one” and indefinitearticles such as “a” or “an.” The same holds true for the use ofdefinite articles. Unless stated otherwise, terms such as “first” and“second” are used to arbitrarily distinguish between the elements suchterms describe. Thus, these terms are not necessarily intended toindicate temporal or other prioritization of such elements. The merefact that certain measures are recited in mutually different claims doesnot indicate that a combination of these measures cannot be used toadvantage.

While certain features of the embodiments of the disclosure have beenillustrated and described herein, many modifications, substitutions,changes, and equivalents will now occur to those of ordinary skill inthe art. It is, therefore, to be understood that the appended claims areintended to cover all such modifications and changes as fall within thetrue spirit of the embodiments of the disclosure.

We claim:
 1. A system for illuminating a substrate, the systemcomprises: acousto-optic devices, wherein each acousto-optic device ofthe acousto-optic devices comprises a surface having an illuminatedregion; optical combining module; and a relay module that images anoutput plane of the optical combining module onto an output aperture ofthe system; wherein illuminated regions of the acousto-optic devices areconfigured to concurrently receive collimated input beams while theacousto-optic devices are concurrently fed with control signals thatcause the illuminated regions to concurrently output illuminated regionsoutput beams that are collimated and exhibit deflection angles thatscan, during a scan period, a deflection angular range; and wherein theoptical combining module is configured to combine the illuminatedregions output beams to provide combined beams, each combined beamcovers a continuous angular range; wherein different combined beamsexhibit, at the output plane of the optical combining module, differentdeflection angles.
 2. The system according to claim 1 wherein the relaymodule comprises a cylindrical lens and a spherical lens, thecylindrical lens is configured convert the combined beams tointermediate collimated beams; wherein different intermediate collimatedbeams impinge on different parts of the spherical lens.
 3. The systemaccording to claim 2 wherein different intermediate collimated beamsimpinge on different locations of the spherical lens, during the scanperiod.
 4. The system according to claim 3 comprising an output aperturethat is located at a front focal plane of the spherical lens; whereinspherical lens is configured output collimated output beams towards theoutput aperture.
 5. The system according to claim 1 comprising an outputmodule that is configured to convert the collimated output beams tospaced apart spots on the substrate.
 6. The system according to claim 5wherein different linear array of spots scan a linear region of thesubstrate during the scan period.
 7. The system according to claim 5where the output module comprises an output Dammann grating and anobjective lens; wherein the output Dammann grating is configured toreceive the collimated output beams, and provide output diffractionpatterns that are converted by the output objective lens to the spacedapart spots.
 8. The system according to claim 5 comprising one or moredetectors that are configured to generate detection signals indicativeof radiation from the substrate that resulted from a formation of thespaced apart spots on the substrate.
 9. The system according to claim 1that is configured to illuminate the substrate during multiplerepetitions of the scan period.
 10. The system according to claim 1comprising a radiation source that is configured to avoid illuminatingthe surfaces that comprise the illuminated regions outside theilluminated regions; wherein an area of each of the illuminated regionis a fraction of an area of each of the surfaces.
 11. A method forilluminating a substrate, the method comprises: illuminating,concurrently, illuminated regions of acousto-optic devices withcollimated input beams while concurrently feeding the acousto-opticdevices with control signals that cause the illuminated regions toconcurrently output illuminated regions output beams that are collimatedand exhibit deflection angles that scan, during a scan period, adeflection angular range; combining, by an optical combining module, theilluminated regions output beams to provide combined beams, eachcombined beam covers a continuous angular range; wherein differentcombined beams exhibit, at an output plane of the optical combiningmodule, different deflection angles; and imaging, by a relay module, theoutput plane of the optical combining module onto an output aperture.12. The method according to claim 11 comprising converting, by acylindrical lens of the relay module, the combined beams to intermediatecollimated beams; wherein different intermediate collimated beamsimpinge on different parts of a spherical lens.
 13. The method accordingto claim 12 wherein different intermediate collimated beams impinge ondifferent locations of the spherical lens of the relay module, duringthe scan period.
 14. The method according to claim 13 wherein the outputaperture that is located at a front focal plane of the spherical lens;wherein the method comprises outputting, by the spherical lens,collimated output beams towards the output aperture.
 15. The methodaccording to claim 11 comprising converting the collimated output beamsto spaced apart spots on the substrate.
 16. The method according toclaim 15 wherein different linear array of spots scan a linear region ofthe substrate during the scan period.
 17. The method according to claim15 where the converting comprises: illuminating an output Dammanngrating with the collimated output beams; outputting, by the outputDammann grating, output diffraction patterns; and converting the outputdiffraction patterns, by an objective lens, to form the spaced apartspots.
 18. The method according to claim 15 comprising obtainingdetection signals indicative of radiation from the substrate thatresulted from a formation of the spaced apart spots on the substrate.19. The method according to claim 11 comprising repeating theilluminating, receiving and converting for each one of multiple scanperiods.
 20. The method according to claim 11 comprising avoiding fromilluminating surfaces that comprise the illuminated region outside theilluminated regions; wherein an area of each of the illuminated regionsis a fraction of an area of each of the surfaces.